Water Resources, class 10

Introduction: 

Three-fourth of the earth’s surface is covered with water, but only a small proportion of it accounts for freshwater that can be put to use. This freshwater is mainly obtained from surface run off and ground water that is continually being renewed and recharged through the hydrological cycle. All water moves within the hydrological cycle ensuring that water is a renewable resource.

Water is a renewable resource as it is renewed by water cycle itself, where three processes take place as evaporation, condensation and precipitation. This process of water cycle is never ending and hence, water is a renewable resource.

Meaning of water scarcity: 

Water scarcity is the lack of sufficient availability of water resources to meet the demands of water usage within a region.

Reasons for water scarcity:

a) Over Exploitation, excessive use and unequal access to water.

b) Water Scarcity is the outcome of large and growing population. A large population means more water for domestic and to produce more food.

c) Water resources are exploited to expand agricultural production, which may lead to decline in ground water level. 

Falling ground water levels is adversely affecting water availability and food security of the people.

d) Industrialization: The ever-increasing number of industries has made matters worse by exerting pressure on existing freshwater resources. Industries, apart from being heavy users of water, also require power to run them. Much of this energy comes from hydroelectric power.

e) Urbanisation: Moreover,multiplying urban centres with large and dense populations and urban lifestyles have not only added to water and energy requirements but have further aggravated the problem.

 Housing societies and colonies have their own groundwater pumping devices to meet their water needs. 

f) There can be scarcity may be due to bad quality of water.Most of the water is polluted by domestic and industrial wastes, chemicals, pesticides, fertilizers etc.

Managing and conserving water resources is the need of the hour

a) To safeguard ourselves from health hazards.

b) To ensure food security.

c) For continuation of our livelihood and productive activities.

d) To prevent the degradation of eco-system.

Hydraulic structure in Ancient India

a) In the first century B.C. at Sringaverapur near Allahabad water harvesting system existed using the flood water from Ganga river.

b) During the time of Chandragupta Maurya, dams, lakes etc. were built.

c) Irrigation works were also found in Kalinga, Nagarjuna Konda, Bennur and Kohlapur.

d) In the 11th Century, Bhopal Lake, one of the largest artificial lakes of its time was built.

e) In the 14th Century, Iltutmish constructed a tank in Hauz Khas (Delhi) for supplying water to Siri fort area.

Dams -

A dam is a large wall or barrier that blocks or stops the flow of water, forming a reservoir or a lake. Most dams have a section called a spillway or weir over which, or through which, water flows, either sometimes or always. 

Dams are classified according to structure, intended purpose or height. 

Based on structure and the materials used, dams are classified as timber dams, embankment dams or masonry dams, with several subtypes. 

According to the height, dams can be categorised as large dams and major dams or alternatively as low dams, medium height dams and high dams.

Multi-purpose river projects- are large dams that serve several purposes in addition to impounding the water of a river and used later to irrigate agricultural fields.

Multipurpose projects apart from supplying water for irrigation and electricity generation also supply water for domestic and industrial uses, flood control, recreation, inland navigation and fish breeding. 

For example, the Sutluj-Beas river basin, the Bhakra-Nangal project etc. 

Advantages of multi-purpose river projects are-

a) Multipurpose projects greatly help in storing water which can be utilized for irrigation.

b) They also help in checking floods. 

c) Provide water supply for domestic and industrial uses.

d) It is helpful in the development of hydroelectricity. 

e) It is also helpful for the tourism industry. Bhakra- Nangal Project on river Satluj is one of the example of multipurpose project.

f) Used for inland navigation and fish breeding.

Disadvantages of Multi-purpose river projects are -

a) It affects the natural flow of river causing poor sediment flow and excessive sedimentation at the bottom of the reservoir. It destroys the habitats for the rivers aquatic life.

b) Dams make it difficult for the aquatic fauna to migrate.

c) Existing vegetation and soils are submerged under water.

d) Building of dams creates large scale displacement of local communities. They have to give up their land, livelihood etc.

e) Floods occur due to the sedimentation in the reservoir and life and property are devastated. 

f) They induced earthquakes, water-borne diseases, pollution from the excessive use of water.

g) Inter-state water disputes are also becoming common with regard to sharing the costs and benefits of the multipurpose project. Eg.- Krishna-Godavari dispute is due to the objections raised by Karnataka and Andhra Pradesh governments. It is regarding the diversion of more water at Koyna by the Maharashtra government for a multipurpose project. This would reduce downstream flow in their states with adverse consequences for agriculture and industry.

h) Irrigation has also changed the cropping pattern of many regions with farmers shifting to water intensive and commercial crops. This has great ecological consequences like salinisation of the soil. At the same time, it has transformed the social landscape i.e. increasing the social gap between the richer landowners and the landless poor. 

i) Dams also create conflicts between people wanting different uses and benefits from the same water resources. In Gujarat, the Sabarmati-basin farmers were agitated and almost caused a riot over the higher priority given to water supply in urban areas, particularly during droughts. 

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Movements against Multi-purpose river projects

Multi-purpose projects and large dams have also been the cause of many new social movements like the ‘Narmada Bachao Andolan’ and the ‘Tehri Dam Andolan’ etc. 

Resistance to these projects has primarily been due to the large-scale displacement of local communities. Local people often had to give up their land, livelihood and their meagre access and control over resources for the greater good of the nation.

Narmada Bachao Andolan or Save Narmada Movement is a Non-Governmental Organisation (NGO) that mobilised tribal people, farmers, environmentalists and human rights activists against the Sardar Sarovar Dam being built across the Narmada river in Gujarat. It originally focused on the environmental issues related to trees that would be submerged under the dam water. Recently it has re-focused the aim to enable poor citizens, especially the displaced people to get full rehabilitation facilities from the government. he Tehri Dam Andolan etc. 

Do you know? 

Sardar Sarovar Dam has been built over the Narmada River in Gujarat. This is one of the largest water resource projects of India covering four states—Maharashtra, Madhya Pradesh, Gujarat and Rajasthan. The Sardar Sarovar project would meet the requirement of water in drought-prone and desert areas of Gujarat (9,490 villages and 173 towns) and Rajasthan (124 villages).

Do you know?

The Krishna-Godavari dispute is due to the objections raised by Karnataka and Andhra Pradesh governments? It is regarding the diversion of more water at Koyna by the Maharashtra government for a multipurpose project. This would reduce downstream flow in their states with adverse consequences for agriculture and Industry.

Water Harvesting-

A) Many though that given the disadvantages and rising resistance against the multi-purpose projects, water harvesting system was a viable alternative, both socio-economically and environmentally. 

b) People had in-depth knowledge of rainfall regimes and soil types and developed wide ranging techniques to harvest rainwater, groundwater, river water and flood water in keeping with the local ecological conditions and their water needs.

c) In hill and mountainous regions, people built diversion channels like the ‘guls’ or ‘kuls’ of the Western Himalayas for agriculture. 

d) ‘Rooftop rain water harvesting’ was commonly practiced to store drinking water, particularly in Rajasthan.

e) In the flood plains of Bengal, people developed inundation channels to irrigate their fields. 

f) In arid and semi-arid regions, agricultural fields were converted into rain fed storage structures that allowed the water to stand and moisten the soil like the ‘khadins’ in Jaisalmer and ‘Johads’ in other parts of Rajasthan. 

g) ‘Rooftop rain water harvesting’ was commonly practiced to store drinking water, particularly in Rajasthan. 

h) In the semi-arid regions of Rajasthan, particularly in Bikaner, Phalodi and Barmer, almost all the houses traditionally had underground tanks for storing drinking water. They were connected to the sloping roofs of the houses through a pipe. 

Rain falling on the roof tops would travel down the pipe and was stored in these underground tanks. 

 The rainwater can be stored in the tanks till the next rainfall making it an extremely reliable source of drinking water when all other sources are dried up, particularly in the summers. 

 Rainwater, or palar pani, as commonly referred to in these parts, is considered the purest form of natural water. 

Today, in western Rajasthan, sadly the practice of rooftop rainwater harvesting is on the decline as plenty of water is available due to the perennial Rajasthan Canal, though some houses still maintain the tankas since they do not like the taste of tap water.

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i) In Meghalaya there is a 200 years old system of tapping stream & spring water by using bamboo pipes.18 to 20 litres of water enters the bamboo pipe, gets transported over 100’s of metres and is reduced to 20 -80 drops per minute at the site of the plant.

METHOD: Bamboo pipes are used to divert perennial springs on the hilltops to lower reaches by gravity. The channel sections made of bamboo divert water to the site where it is distributed into branches made of bamboo pipes. 

The water flow is manipulated by changing the position of the pipes. At the last stage, the channel sections & diversion units are reduced. The last channel section helps water to be dropped near the roots of the plant.

 Rain water harvesting: Examples in India: 

a) In Gendathur, a remote backward village in Mysore, Karnataka, villagers have installed, in their household’s rooftop, rainwater harvesting system to meet their water needs. Nearly 200 households have installed this system and the village has earned the rare distinction of being rich in rainwater.

b) Tamil Nadu is the first and the only state in India which has made roof top rainwater harvesting structure compulsory to all the houses across the state. There are legal provisions to punish the defaulters.

c) Roof top rain water harvesting is the most common practice in Shillong, Meghalaya. It is interesting because Cherapunjee and Mawsynram situated at a distance of 55 km. from Shillong receive the highest.rainfall in the world, yet the state capital Shillong faces acute shortage of water. Nearly every household in the city has a roof top rain water harvesting structure. Nearly 15-25 per cent of the total water requirement of the household comes from roof top water harvesting.